Wax-resin-hydroxypropyl cellulose thermofluid vehicles

ABSTRACT

THERMOFLUID VEHICLES OF THE WAX-RESIN TYPE FOR VITREOUS ENAMEL COLOR COMPOSITIONS ARE DESCRIBED. THE VEHICLES CONTAIN A FATTY ALCOHOL OF FATTY AMIDE WAX, A RESIN BINDER AND A SMALL AMOUNT OF HYDROXYPROPYL CELLULOSE AND GIVE, WITH ENAMEL COLORS, COMPOSITIONS WHICH DO NOT RUN OR SAG DURING FIRING AND WHICH PRODUCE ENAMEL COATINGS FREE OF STENCIL MARKINGS.

United States Patent 3,639,310 WAX-RESIN-HYDROXYPROPYL CELLULOSETHERMOFLUID VEHICLES Ray Andrews, Washington, Pa., assignor to HerculesIncorporated, Wilmington, Del.

No Drawing. Filed Feb. 16, 1970, Ser. No. 11,845 Int. Cl. C03c J/OO U.S.Cl. 260-17 R 2 Claims ABSTRACT OF THE DISCLOSURE Thermofluid vehicles ofthe wax-resin type for vitreous enamel color compositions are described.The vehicles contain a fatty alcohol or fatty amide wax, a resin binderand a small amount of hydroxypropyl cellulose and give, with enamelcolors, compositions which do not run or sag during firing and whichproduce enamel coatings free of stencil markings.

This invention relates to vehicles for vitreous enamel colorcompositions and more particularly to improved thermofluid vehicles ofthe wax-resin type.

Thermofluid wax-containing vehicles for enamel coating compositions tobe applied to base objects by slik or metal screen stencil processes areknown. The major problem encountered in the use of these vehicles is runoff or sagging from the coated area during firing, and the retention ofscreen markings on the fired enamel coated object.

Various materials such as the anionic surface active agent which is thereaction product of phosphoryl chloride and a fatty alcohol, ethylcellulose, azelaic acid and the like have been suggested as additives towax-containing vehicles for enamel coating compositions to improvestiffness or viscosity at firing temperatures and to prevent running andscreen markings. Although such additives improve the performance of thecoatings under normal firing conditions, running and sagging still occurunder the conditions required for decorating glassware and particularlysham bottom tumblers which have thin sidewalls and heavy bottoms.Additionally, stencil markings are not smoothed out or eliminated sothat irregularities persist on the coated surfaces. Moreover, the enamelcoatings do not overprint themselves well and different vehicles arerequired for each coolr coating to obtain commercially acceptablemulti-color or multi-tone effects. Overprinting is a particularlydesirable property when mat colors and/ or gold effects are required.

It is an object of this invention to provide thermofluid wax-containingvehicles for use ,with vitreous enamel color compositions which, whenapplied to glassware, will not run or sag during firing and which willproduce enamel coatings free of stencil markings. Another object of thisinvention is to provide a thermofluid vehicle which can be used inmulti-color decoration and will over-print itself well.

Now, in accordance with this invention it has been found that the aboveobjects can be realized by vitreous enamel color vehicles comprising byweight (a) 50 to 80% of a normally solid wax-like material selected fromthe group consisting of straight chain alcohols having 16 to 20 carbonatoms, amides of aliphatic hydrocarbons containing 16 to 20 carbon atomsand mixtures thereof; (b) 8 to 38% of a resinous binder soluble in saidwax-like material; and (c) l to 12% of hydroxypropyl cellulose having anMS. of at least 2.

By the expression normally solid wax-like material is meant a materialhaving the characteristics of wax and non-tacky solidity at roomtemperature (25 C.) but ready fusibility at above about 50 C. Thewax-like materials which are suitable as vehicle constituents inaccordance with this invention are, as stated, the substantiallystraight chain alcohols having 16 to 20 ,carbon atoms such as 3,639,310Patented Feb. 1, 1972 stearyl alcohol, cetyl alcohol and mixtures ofsuch alcohols; the amides of aliphatic hydrocarbons containing 16 to 20carbon atoms such as the amides of hexadecane, octadecane, octadecaneand mixtures thereof; and mixtures of any of the above alcohols andamides. The wax-like material constitutes the bulk of the vehicle and ispresent within the range of 50 to 80% and preferably from about 60 toabout by weight of the vehicle.

The vehicle also contains, as stated above, from 1 to 12% and preferablyfrom 2 to 10% by weight of hydroxypropyl cellulose having an MS. (molarsubstitution) of at least 2. Such hydroxypropyl celluloses are describedin U.S. Pat. 3,278,521 to Klug and are normally solids which are solublein cold water, insoluble in hot water, and soluble in polar organicsolvents. The preferred hydroxypropyl celluloses will generally have anMS. of 2 to 10 and preferably in the range of from about 3 to about 5.They are commercially available in finely divided condition under theKlucel trademark in different viscosity grades. While any of theseviscosity grades can be used in the practice of the invention, the lowerviscosity grades such as grades I, L and E are preferred. Best resultsare obtained with Klucel E having an MS. of 2.8 to 4.0 and preferably3.0 to 3.7 and a viscosity of 200 to 300 centipoises measured at 25 C.on a 10% aqueous solution.

In addition to the wax component and the hydroxypropyl cellulose, thevehicle also contains from 8 to 38% and preferably from 10 to 30% of aresinous binder which is soluble in the wax. The binder can be one ormore of the conventional resinous additives known to modify or improvethe hardness, toughness, viscosity, bonding properties, pigment andglass Wettability, etc. of thermofluid vehicles. For example the binderwill usually comprise about 33% of one or more thermoplastic materialswhich provide a wetting action for pigment and glass, about 33% of oneor more thermoplastic materials which contribute coherence and toughnessand about 33% of one or more thermoplastic materials which maintain theviscosity Within a desired range. Useful materials which can be used asthe binder component include thermoplastic resins such as rosin; amodified rosin such as hydrogenated rosin and disproportionated rosin; arosin derivative such as a rosin ester; polymers of the resin acids orrosin; synthetic rubbers; alkyd resins; acrylate and methacrylate resinssuch as n-butyl methacrylate; the resinous chlorinated diphenyls;styrene resins; ethyl cellulose; and mixtures thereof. Other polymericmaterials which are more Waxlike than resinous can also be present forspecial effects such as dispersibiilty, plasticization, lubricity, etc.Particularly preferred materials of this type are the polyalkylene etherglycols such as the polymethylene ether glycols and the polyethyleneether glycols having an average molecular weight of at least about 4000and preferably from about 4000 to 6000. Best results are obtained whenthe vehicle contains in addition to the wax component and thehydroxypropyl cellulose as binder, 3 to 12% of rosin, modified rosin ora rosin ester, 3 to 12% of styrene resin, 2 to 12% of an acrylate resin,0.5 5to 5% of ethyl cellulose and 0 to 8% of a polyalkylene etherglycol, the total of the above ingredients not exceeding 38% of thevehicle.

The thermofluid vehicle of the invention can be employed in variousamounts with respect to the ceramic or enamel color-constituents of theenamel coating compositions. Generally, the proportion of vehicle toenamel color will be between 1:2 and 1:5.

The ceramic or enamel color constituents of the enamel coating are anyof the vitrifiable compositions customarily employed in ceramic glazeapplications, and generally consist of about 5 to 20% of inorganic oxidepigments and from about 95 to of finely-divided lead borosilicate glassfrit.

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The enamel color constituents and vehicle can be compounded in anyconvenient manner and the resulting enamel color composition applied toan object to be decorated conventionally, as through a screen stencil bymeans of a squeegee process at a temperature above the melting point ofthe vehicle. The coated object is then fired at a temperature which willfuse the enamel color and thereby produce a firmly bonded design on theobject. The firing temperature will usually range from about 550 to 650C. If desired, a plurality of color compositions in any desired registrycan be superimposed upon each other before carrying out the firingoperation.

The invention is further illustrated by the following examples. Allparts and percentages are by weight unless otherwise indicated.

EXAMPLE 1 A resin-wax vehicle is prepared by stirring at 165 C. untilhomogeneous the following ingredients:

n-Butyl methacrylate resin 8 Polystyrene (low molecular weight, soft,plasticizing resin having a Ball and Ring melting point of 75 C.Hydrogenated rosin (softening point of 75 C.) Ethyl cellulose 1Hydroxypropyl cellulose (M.S. of 3.0-3.7, viscosity of 200-300 cps. at25 C. as measured on a 10% by weight aqueous solution) 6 1 Ethoxylcontent of 47.5 to 49.0%, a degree of substitution of 2.42-2.53 and aviscosity of 200 cps. at 25 C. measured on a. 5% by weight solution in80 20 toluene: ethanol by weight on sample dried 30 minutes at 100 C.The above vehicle is mixed with 500 parts of a glass color comprising85% of a lead borosilicate glass flux and of titanium dioxide pigment(both being of a particle size substantially finer than the decoratingscreen through which they will pass) at 100 C., applied as a decorativecoating on sham bottom glass tumblers by metal screen printing and thenfired at 600 C. for 15 minutes. The coating is free of irregularitiesand screen marks and no running or sagging is encountered during firing.

When a vehicle is prepared in the same manner except that nohydroxypropyl cellulose is present and the amount of ethyl cellulose isincreased to 7 parts, the decorated glassware is inferior, running andsagging having occurred during firing and screen marks being present onthe surface of the coating.

EXAMPLE 2 The procedure of Example 1 is repeated except that the vehicleadditionally contains 5 parts of a polyethylene 4 ether glycol having amolecular weight of about 4000, and 5 parts of n-butyl methacrylateresin, 4 parts of polystyrene and 4 parts of hydrogenated rosin areused. Excellent coatings which do not run or sag on firing and are freeof stencil marks are produced.

EXAMPLE 3 The general procedure of Example 1 is repeated except that amulti-color decoration is applied to the glass tumblers prior to firingby overprinting different color compositions prepared with the vehicleof Example 1. In overprinting, each successive print decoration issuperimposed, at least in part, over a prior print decoration. Excellentfinal decorations of multi-color design result with no running of coloror sagging and no screen marks when 2, 3, 5 and 8 layers of decorationare employed.

What I claim and desire to protect by Letters Patent is: 1. Athermofluid vehicle for vitreous enamel color compositions comprising byweight (a) 50 to of a normally solid wax-like material selected from thegroup consisting of straight chain alcohols having 16 to 20 carbonatoms, amides of aliphatic hydrocarbons containing 16 to 20 carbon atomsand mixtures thereof; (b) a resinous binder soluble in said wax-likematerial and comprising 3 to 12% of rosin, modified rosin or a rosinderivative, 3 to 12% of a styrene resin, 2 to 12% of an acrylate resin,0.5 to 5% of ethyl cellulose and 0 to 8% of a polyalkylene glycol ether,the sum thereof not exceeding 38% by weight of the vehicle; and 1 (c) 1to 12% of hydroxypropyl cellulose having a molar substitution of atleast 2.

2. The vehicle of claim 1 wherein the modified rosin is hydrogenatedrosin.

References Cited UNITED STATES PATENTS 2,379,507 7/ 1945 Deyrup 260-162,607,701 8/1952 Jessen 106-123 2,617,704 11/1952 Morris 106-3112,823,138 2/1958 Hoflman 106311 3,084,129 4/1963 Hoffman 26017 R3,089,782 5/1963 Bush et a1 1l7-38 3,414,417 12/ 1968 Miller et al 10626WILLIAM H. SHORT, Primary Examiner L. M. PHYNES, Assistant Examiner US.Cl. X.R. 106-26, 173; 26027, 28.5

